Studies I've read (abstract at any rate) indicates 3-4 hours was not enough. They ended up doing 14 hours / day or so. Not sure if that is even doable in a tour, so much phaffing around with transfers, etc.

I don't think I saw any studies where they did 14 hrs/day for 2-3 weeks to boost Hgb then followed with 3-4hrs / day maintenance though, that'd be interesting.

Did you see that study where altitude training (LHTL) was found to increase testosterone production? I went looking after reading Aldo Sassi apparently saying that was one effect of altitude training to a journalist who was discussing Sky's altitude training camps (the same guy who said they don't care about Hgb increases).

It felt more likely to me that riders were using it to help with recovery when training at altitude and the researchers were just recording test levels, and not looking or able to differentiate exo from endo-genous.

The whole issue with altitude training is that it is almost a "Black Art" to determine the right level, then there are also sleep issues, particularly in a tent.

I did not see the study on altitude increasing T, but since in males T modulates RBC, it does make sense...

I think some are on to intermittent hyperoxia -- both the training effect and the paradoxical increase in RBC....